How to Create a Custom ROM With Root Access For Windows Phone Internals

Heathcliff74 announced that Windows Phone Internals
support most versions of Windows Phone 8.1 and Windows 10 Mobile. These
two operating systems are shipped with most currently available Lumia
phones. There is a great chance that your device might be supported and
you can unlock your phone.

There are two detailed videos on which Heatcliff74 shows
how to use his tool. While it looks simple, you should use this tool
with caution. Messing around with bootloaders is always risky, so there
is always a chance to hard brick your device.